Rotor Configuration Which Reduces Copper Loss of Switched Reluctance Motors with Suppression of Torque Ripple and Input Current Ripple

Switched reluctance motors (SRMs) are attractive motors for electric vehicle propulsion because of their cost-effectiveness or robust structures. However, SRMs suffer from input current ripple and torque ripple. The authors have proposed derivation method of phase current profile which suppresses input current ripple and torque ripple and experimentally verified the suppression of both ripples. However, the rms value of derived phase current was much greater than square wave current, which is implemented widely, and increased copper loss. For the EV application, the rms value should be reduced. To break through the issue, the author addressed the characteristic that phase current profiles are shaped based on each reluctance profile, which is shaped by motor configuration, and noticed that phase current profile with low rms value may be derived by a novel rotor configuration. Therefore, this paper proposes a novel rotor configuration which can reduce the copper loss. The proposed rotor configuration is designed to satisfy the reluctance profile which is derived by previously proposed derivation method of phase current. This paper also presents the experiment for the evaluation of the reduction of copper loss.

I. Introduction

Recently, electric vehicles (EVs) are widely used because they are environmentally friendly. In almost all the EVs, permanent magnet motors are adopted for propulsion. However, the permanent magnet motors are expensive because of the rare metal contained in the permanent magnets. To reduce the EV cost, propulsion motors should not be expensive.